1. Field of the Invention
The present invention relates to electronic components, and more particularly, to electronic components including built-in coils.
2. Description of the Related Art
The multilayer coil component described in Japanese Unexamined Patent Application Publication No. 10-270249 is a known example of an existing electronic component. In this multilayer coil component, a multilayer body having a rectangular parallelepiped shape is formed of a plurality of insulating green sheets stacked on top of one another. Coil conductors are provided on the plurality of insulating green sheets. The coil conductors are connected to one another through via holes, thereby forming a helical coil. Furthermore, two terminal electrodes are arranged so as to cover two side surfaces of the multilayer body and the helical coil is connected to two terminal electrodes.
In the multilayer coil component described in Japanese Unexamined Patent Application Publication No. 10-270249, the terminal electrodes are arranged so as to cover the side surfaces of the multilayer body and, therefore, are arranged side by side with and close to each of the coil conductors in a direction perpendicular to the stacking direction. Consequently, floating capacitances occur between the coil conductors and the terminal electrodes. When such floating capacitances occur, there is a problem in that the resonant frequency of the coil is decreased and the Q value at a frequency at which the coil is to be used is decreased. Therefore, the generation of floating capacitances in multilayer coil components decreases the Q values of electronic components that include built-in coils.
An electronic component 500 including a land grid array (LGA) structure illustrated in FIG. 7 is an example of an electronic component that is capable of suppressing the generation of floating capacitances. FIG. 7 is an exploded perspective view of the electronic component 500. Hereafter, the stacking direction of the electronic component 500 is defined as a z-axis direction, a direction in which longer edges of the electronic component 500 extend is defined as an x-axis direction, and a direction in which shorter edges of the electronic component 500 extend is defined as a y-axis direction. The x-axis, the y-axis, and the z-axis are orthogonal to one another.
The electronic component 500 includes a multilayer body 502, external electrodes 506a and 506b, and coils L501 and L502. The multilayer body 502 includes rectangular insulator layers 504a to 504i that are stacked on top of one another. Coil electrodes 508a to 508e provided on the insulator layers 504d to 504h are connected to one another through via hole conductors B thereby forming the coil L501. Furthermore, coil electrodes 510a to 510e provided on the insulator layers 504d to 504h are connected to one another through the via hole conductors B, thereby forming the coil L502. In addition, the coil electrode 508a and the coil electrode 510a are connected to each other, and thereby the coil L501 and the coil L502 are connected to each other.
Furthermore, the external electrodes 506a and 506b are provided on a surface of the multilayer body 502 on the negative side in the z-axis direction and are respectively connected to the coil electrodes 508e and 510e through the via hole conductors B. In the electronic component 500, the external electrodes 506a and 506b are provided on a surface of the multilayer body 502 on the negative side in the z-axis direction and, therefore, are not close to or side by side with the coil electrodes 508a to 508d and 510a to 510d. Therefore, a decrease in the Q value of the electronic component 500 due to the generation of floating capacitances between the external electrodes 506a and 506b, and the coil electrodes 508a to 508d and 510a to 510d is prevented.
However, there is a problem with the electronic component 500 illustrated in FIG. 7 in that it is difficult to obtain a high Q value. In more detail, in the electronic component 500, the coil electrodes 508 and 510 are arranged so as to be side by side on the same insulator layers 504. Consequently, in the electronic component 500, the inner diameters of the coil electrodes 508 and 510 are smaller than when a single coil electrode is provided on an insulator layer. Thus, if the inner diameters of the coil electrodes 508 and 510 are smaller, the amounts of magnetic flux passing through the inside of the coil electrodes 508 and 510 are also smaller and the inductance values of the coils L501 and L502 are decreased. Consequently, in order to obtain a desired inductance value, it is necessary to increase the lengths of the coil electrodes 508 and 510. However, if the lengths of the coil electrodes 508 and 510 are increased, the resistance is increased and the Q value is decreased.
In addition, an electronic component in which two coils are arranged in parallel with each other as illustrated in FIG. 7 is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 9-63848. However, in the multilayer inductor disclosed in Japanese Unexamined Patent Application Publication No. 9-63848, two coils are arranged in parallel with each other and, therefore, the same problem as that described with respect to the electronic component 500 illustrated in FIG. 7 occurs. Furthermore, since external electrodes are provided on side surfaces of the multilayer body, the multilayer inductor described in Japanese Unexamined Patent Application Publication No. 9-63848 also has the problem of the Q value being decreased due to the increased floating capacitance.